1. Field of the Invention
The present invention relates generally to medical devices and methods. In particular, the present invention relates to a system, device and method for managing saliva accumulation in an oral device that may be held in the mouth of a patient to reduce the incidence of obstructive sleep apnea or snoring or for other purposes.
Obstructive sleep apnea (OSA) is a serious medical condition resulting from a temporary airway blockage which occurs as a patient sleeps. The airway blockage usually occurs between the soft palate and/or the back of the tongue and the pharynx. As the patient breathes, the reduced area in the upper airway can cause snoring, and more seriously, OSA.
Sleep disruption caused by OSA can result in severe daytime sleepiness, chronic fatigue, headaches, depression, accidents, injuries, and of particular concern, OSA can reduce the amount of oxygen entering the lungs causing hypoxia. Hypoxia, in turn, can lead to pulmonary hypertension, heart disease, and stroke.
Numerous invasive and less invasive treatments have been proposed for OSA. Of particular interest to the present invention, “continuous positive airway pressure” (CPAP) delivers a continuous stream of pressurized air directly to the person's upper airway. The positive pressure maintains patency of the airway and inhibits the collapse associated with OSA. Although generally effective, CPAP suffers from a number of drawbacks that have led to a high level of non-compliance. The patient must wear a bulky facial mask which can be uncomfortable, and the system generates noise that can make falling asleep difficult. CPAP is also difficult to use because the mask requires careful fitting to avoid air leaks and facial discomfort and because the mask can easily be dislodged during sleep. Moreover, a number of unpleasant side effects, such as sore throats, dry throat and eyes, headaches, and skin rashes from the mask frequently occur. These problems have resulted in a high level of non-compliance with CPAP therapy.
As an improvement over CPAP, it has been proposed to apply a negative pressure to the patient's oral cavity. For example, devices have been proposed which apply a vacuum at the forward end of the patient's mouth, typically at or just behind the lips, to pull the tongue forward in order to lift the rear portion of the tongue away from the back of the airway. See, for example, U.S. Patent Publication Nos. 2007/0277818, 2005/0166928 and 2005/0166929. As an improvement over these devices, it has more recently been proposed to apply a negative pressure in region or space above the tongue which in turn draws the soft palate away from the pharynx to draw the rear portion of the tongue away from the pharynx as well. See, commonly owned U.S. Patent Publication Nos. 2009/0120446 and 2009/0120447.
With all such oral devices, saliva can accumulate in the vacuum lines and vacuum pump connected to the oral device. While it is proposed in commonly owned U.S. Patent Publication No. 2009/0123886 to collect saliva from the vacuum lines using a liquid trap in the connecting line between the oral device and the pump, the saliva can still collect in the connecting line and result in an unpredictable additional pressure drop between the pump and the oral device. To help clear the connecting line, it is further proposed to provide a positive pressure pump to introduce air to the oral cavity or to connect an air bleed line to the remote end of the vacuum line to allow a continuous air circulation. Even these measures, however, have not been entirely effective in removing saliva from the system to eliminate blockages and unpredictable pressure drops. In particular, saliva can still accumulate in the oral device itself which can increase the actual pressure drop in ways that are difficult to predict and address.
For these reasons, it would be desirable to provide alternative and improved methods and apparatus for drawing a vacuum in a patient's oral cavity for treating obstructive sleep apnea and other purposes. The methods and devices should be effective both in clearing saliva from the vacuum connecting line and in keeping the oral device free of accumulated saliva. The methods and systems should be simple and inexpensive to implement and add little or no complexity to the control system At least some of these objectives will be met by the inventions described below.
2. Description of the Background Art
Commonly owned U.S. Patent Publication Nos. 2009/0120446; 2009/0120447; and 2009/0123886, have been described above. Oral and external devices for treating sleep apnea and snoring are described in U.S. Patent Publication Nos. US2005/166929; US2005/166928; US2008/0188947; US2007/0277818; US2008/0216843; and US2008/0210244; and in U.S. Pat. Nos. 7,182,082; 7,073,506; 7,073,505; 6,955,172; 6,877,513; 6,494,209; 5,957,133; 5,465,734; 4,676,240; 4,304,227; 4,169,473; and 3,132,647; and in Cartwright and Samelson “The effects of a non-surgical treatment for obstructive sleep apnea: the tongue retaining device;” Journal of the American Medical Association 248 (1982).